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The antimicrobial peptide Enterocin CRL35, a class II bacteriocin, produces at high concentrations (8 microg ml(-1)) localized holes in the wall and cellular membrane of Listeria monocytogenes, reflected in the efflux of macromolecules such as proteins and other ultraviolet-absorbing materials. At lower concentrations (0.5 microg ml(-1)), neither ultra structural changes nor macromolecules efflux were observed, however potassium and phosphate ions were released, dissipating the proton motive force. As a result the bacteria were killed.

The Lactococcus lactis subsp. lactis biovar diacetylactis citrate permease P is encoded by the citP gene borne by an 8.3-kb Cit+ plasmid (F. Sesma, Gardiol, D., de Ruiz Holgado, A.P. and de Mendoza, D., Appl. Environ. Microbiol. 56 (1990) 2099–2103). By subcloning different DNA fragments from the Cit+ plasmid it was found that citP is the only plasmidic gene required for the transport of citrate. Northern blot analysis revealed that citP is transcribed in two mRNA species with lengths of 2.9 and 1.9 kb. The transcriptional pattern, the total amount of citP mRNAs and the transport of citrate were unaffected by the presence of citrate in the growth media. Our results support the conclusion that transcription of citP as well as citrate transport are not induced by citrate in Lactococcus lactis subsp. lactis biovar diacetylactis.